Investigation the solidification of Al-4.8 wt.%Cu alloy at different cooling rate by computer-aided cooling curve analysis

Depending on the casting conditions and alloy composition, microstructure and properties of the aluminium alloys will be different. There are many techniques available for investigating the solidification of metals and alloys. In recent years computer-aided cooling curve analysis (CA-CCA) has been used to determine thermophysical properties of alloys, latent heat and solid fraction. The aim of this study was to investigate the effect of cooling rate on the structural features of Al-4.8 wt.%Cu alloy by thermal analysis of cooling curves. To do this, Al-4.8 wt.%Cu alloy was melted and solidified applying 0.04, 0.42, and 1.08 °C/sec cooling rates. The temperature of the samples was recorded using a K thermocouple and a data acquisition system connected to a PC. It was found that the formation temperatures of various thermal parameters such as (liquidus, solidus and eutectic temperatures) are shifting by increasing of cooling rate from 0.04 °C/sec to 1.08 °C/sec. The structural results show that grain size and secondary dendrite arm spacing decreased by increasing of cooling rate.  http://dx.doi.org/10.5937/metmateng1402107

Grain size control in al-4.8 wt.% Cu alloy by computeraided cooling curve analysis

Generally Al–Ti and Al–Ti–B master alloys are added to the aluminium alloys for grain refinement. The cooling curve analysis (CCA) has been used extensively in metal casting industry to predict microstructure constituents, grain refinement and to calculate the latent heat of solidification. The aim of this study was to investigate the effect of grain refinement on the grain size of Al-4.8 wt.%Cu alloy by cooling curve analysis. To do this, alloy was grain refined by different amount of Al-5Ti-1B master alloy and all samples were solidified at constant cooling rate of 0.19 ℃/s. The temperature of the samples was recorded using a K thermocouple and a data acquisition system connected to a PC. The results show that the segregating power of Ti is very high and it segregates to the nucleant–liquid interface which leads to constitutional supercooling within which other nucleant particles get activated for nucleation. Other results show that with considering the changes in the primary undercooling (ΔTRU) as the main factor to determine the effectiveness of grain refinement process, it was found that by grain refinement, the value of undercooling decrease was approximately zero. http://dx.doi.org/10.5937/metmateng1403183

Cooling curve analysis in binary Al-Cu alloys: Part II- Effect of Cooling Rate and Grain Refinement on The Thermal and Thermodynamic Characteristics

The Al-Cu alloys have been widely used in aerospace, automobile, and airplane applications. Generally Al-Ti and Al-Ti-B master alloys are added to the aluminium alloys for grain refinement. The cooling curve analysis (CCA) has been used extensively in metal casting industry to predict microstructure constituents, grain refinement and to calculate the latent heat of solidification. The aim of this study is to investigate the effect of cooling rate and grain refinement on the thermal and thermodynamic characteristics of Al-Cu alloys by cooling curve analysis. To do this, Al-Cu alloys containing 3.7, and 4.8 wt.% Cu were melted and solidified with 0.04, 0.19, 0.42, and 1.08 K/s cooling rates. The temperature of the samples was recorded using a K thermocouple and a data acquisition system connected to a PC. Some samples were Grain refined by Al-5Ti-1B to see the effect of grain refinement on the aforementioned properties. The results show that, in a well refined alloy, nucleation will occur in a shorter time, and a undercooling approximately decreases to zero. The other results show that, with considering the cooling rate being around 0.1 °C/s, the Newtonian method is efficient in calculating the latent heat of solidification

Investigation the solidification of Al-4.8 wt.%Cu alloy at different cooling rate by computer-aided cooling curve analysis

Depending on the casting conditions and alloy composition, microstructure and properties of the aluminium alloys will be different. There are many techniques available for investigating the solidification of metals and alloys. In recent years computer-aided cooling curve analysis (CA-CCA) has been used to determine thermophysical properties of alloys, latent heat and solid fraction. The aim of this study was to investigate the effect of cooling rate on the structural features of Al-4.8 wt.%Cu alloy by thermal analysis of cooling curves. To do this, Al-4.8 wt.%Cu alloy was melted and solidified applying 0.04, 0.42, and 1.08 °C/sec cooling rates. The temperature of the samples was recorded using a K thermocouple and a data acquisition system connected to a PC. It was found that the formation temperatures of various thermal parameters such as (liquidus, solidus and eutectic temperatures) are shifting by increasing of cooling rate from 0.04 °C/sec to 1.08 °C/sec. The structural results show that grain size and secondary dendrite arm spacing decreased by increasing of cooling rate. http://dx.doi.org/10.5937/metmateng1402107

Solidification and re-melting phenomena during slurry preparation using the RheoMetal™ process

The melting sequence of the enthalpy exchange material (EEM) and formation of a slurry in the RheoMetal™ process was investigated. The EEM was extracted and quenched, together with a portion of the slurry at different processing times before complete melting. The EEM initially increased in size/diameter due to melt freezing onto its surface, forming a freeze-on layer. The initial growth of this layer was followed by a period of a constant diameter of the EEM with subsequent melting and decrease of diameter. Microstructural characterization of the size and morphology of different phases in the EEM and in the freeze-on layer was made. Dendritic equiaxed grains and eutectic regions containing Si particles and Cu-bearing particles and Fe-rich particles were observed in the as-cast EEM. The freeze-on layer consisted of dendritic aluminum tilted by about 30 deg in the upstream direction, caused by the rotation of the EEM. Energy dispersion spectroscopy analysis showed that the freeze-on layer had a composition corresponding to an alloy with higher melting point than the EEM and thus shielding the EEM from the surrounding melt. Microstructural changes in the EEM showed that temperature rapidly increased to 768 K (495 °C), indicated by incipient melting of the lowest temperature melting eutectic in triple junction grain boundary regions with Al2Cu and Al5Mg8Si6Cu2 phases present. As the EEM temperature increased further the binary Al-Si eutectic started to melt to form a region of a fully developed coherent mushy state. Experimental results and a thermal model indicated that as the dendrites spheroidized near to the interface at the EEM/freeze-on layer reached a mushy state with 25 pct solid fraction, coherency was lost and disintegration of the freeze-on layer took place. Subsequently, in the absence of the shielding effect from the freeze-on Layer, the EEM continued to disintegrate with a coherency limit of a solid fraction estimated to be 50 pct

Microstructural and mechanical properties of friction stir welded Cu-30Zn brass alloy at various feed speeds: Influence of stir bands

In this study, the effect of various feed speeds on microstructure and mechanical properties of friction stir welded Cu–30Zn brass alloy is investigated. Rotation speed was fixed at 950rpm and feed speed varied in the range of 190–375mm/min. Examination of the microstructure showed very fine grains with some deformed grains in the stirred zone and some coarser grains in the thermo-mechanically affected zone and base metal. A unique deformation pattern, namely “stir band” in the stirred zone region was identified and its density increased by increase in feed speed. Results showed that the grain size profile was independent of feed speed and the hardness values decreased by increase in feed speed. Increase in feed speed led to a slight improvement of yield strength and ultimate tensile strength, associated to continuous spring-like morphology of stir bands acting as a strengthening structure. However, ductility reduces considerably from 57 to 27%. Moreover, it is observed that during tensile test, fracture cracks originate exactly adjacent to the stir bands

Facile synthesis of copper oxide nanoparticles using copper hydroxide by mechanochemical process

A facile mechanochemical-based method for synthesis of copper oxide (CuO) nanoparticles is here by introduced. For this purpose, copper hydroxide powder was synthesized through a facile solution method (CuSO4 + 2 Na(OH) → Cu(OH)2 + Na2SO4) after which milling of as-prepared Cu(OH)2 precursor and NaCl resulted in the mechanochemical dehydration of Cu(OH)2 and dispersion of CuO nanoparticles into the salt matrix (Cu(OH)2+2NaCl=CuCl2+2NaOH and then CuCl2+2NaOH=CuO+2NaCl+H2O). Subsequently, washing the milled powders led to the removal of salt matrix and separation of CuO particles. The main advantages of the introduced method are synthesis of CuO nanoparticles with narrow size distribution without subsequent annealing during the process. The results of X-ray diffraction (XRD) indicated that the dehydration of Cu(OH)2 into CuO was completed after three hours of milling. Structural analysis using scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM) and particle size analyzer (PSA) showed that CuO particles had moderately equiaxed shape with sizes ranging from 10-27 nm. Also, the results of UV–visible absorption spectroscopy indicated that CuO nanoparticles had a band gap of 2.5 eV

Establishing a correlation between interfacial microstructures and corrosion initiation sites in Al/Cu joints by SEM-EDS and AFM-SKPFM

A lap joint of AA3003 and pure copper was produced by friction stir welding and the induced interfaces were investigated. Interfacial regions were characterized by SEM–EDS, AFM, SKPFM, OM and Vickers micro-hardness. Multimodal Gaussian distribution (for characterization of surface potential patterns) showed the formation of multiple compounds. A quantitative correlation between microstructure constituents and Volta potential distribution was recognized and confirmed by corrosion attacked sites observations. It was observed that the Al-rich regions proximate the dispersed Cu particles and Cu–Al intermetallics were most susceptible to corrosion attack initiation due to a galvanic driving force between these surface constituents